Single tube hydraulic shock absorber



May 12, 1964 w.zE1DLER SINGLE TUBE HYDRAULIC SHOCK ABSORBER Original Filed April 23, 1959 a .d M v 2 f Q 1 `.lii |||||H|||| I|| H.HH|\ llIIl r 4 .0 D u l 7 /VV//A m Zea 21,26/n

United States Patent O SINGLE TUBE HYDRAULIC SHOCK ABSQRBER Willi Zeidler, Dusseldorf, Germany, assignor to Firma Rheinmetall G.m.b.H., Dusseldorf, Germany Original application Apr. 23, 1959, Ser. No. 808,424, now Patent No. 3,056,473, dated Oct. 2, 1962. Divided and this application Aug. 3, 1962, Ser. No. 214,713

Claims priority, application Germany Apr. 30, 1958 4 Claims. (Cl. 18S-88) The invention relates to a single tube hydraulic shock absorber and is a division of the copending application Serial No. 808,424, iiled April 23, 1959, Patent No. 3,056,473 issued October 2, 1962.

-In said Patent No. 3,056,473 there is described a hydraulic shock absorber particularly for power vehicles and constructed so that there is a through ow space between fthe piston and the cylinder wall for the damping lluid to ilow controlled by plate valves. 'I'hese plate valves are under the inuence of a foam material having closed pores of such structure that theseI foam material members are inuenced by temperature changes in the damping fluid with the area of the passages controlled by -the plate valves in `such a way that by equal dammed-up pressure with increasing temperature, the area of the passages will diminish. The foam material inserts subject to temperature variations will be provided in grooves of the piston sur-faces.

It is an object of the present invention to provide a piston structure which will include means yto compensate yfor lvariations of temperature of the damping Huid. A further object of the invention resides in the piston structure in which a foam cushion is enclosed in a housing separating it from the cylinder Wall and the piston rod, providing a temperature sensitive element, e.g., an air, gas or liquid lled bag or a foam `cushion with closed pores, between the side of said housing facing the piston rod and the lpiston rod itself, such bag governing the clearance space for the ow of liquid between the inside surface of the housing and the piston rod.

Further objects will be -apparent from the following description when considered in connection with the accompanying drawing which is a longitudinal section through the piston, the piston rod and the cylinder.

The foam cushion lila is enclosed by a casing 13 separating i-t from the inner wall of the cylinder and the piston rod 3a, the casing having apertures 14, 15 and 16. These apertures |14 and 15 are closed by ap valves 17 and 18 which operate in the manner of non-return valves whose travel upwards or downwards respectively is limited by discs 19 and 20. The discs 19 and 20 are also used as supports for the piston rings 20a, which are of U-shaped cross Asection and are conveniently made of plastic material and have apertures 21 and 22 through which the damping liquid can pass. 'Ihe ow of liquid from one side of the piston to the other, and hence the characteristic performance of the shock absorber, are regulated by a exible tube 23v which can be filled with air, gas or a liquid. Ata given temperature of the damping uid there is a clearance 25 of a certain cross sectional area between the flexible tube and the inner surface 24 of the casing '13. As the temperature of the damping liquid rises, the iluid inside the exble tube 23 will increase in volume so that the clearance 25 decreases in area, the dynamic pressure remaining fthe same. In order to make it possible to adapt the width of the clearance to the required conditions in any given case easily 3,132,725 Patented May`v l2, l1964 ICC and without dismantling the dashpot, the space enclosed by Ithe flexible tube 23 is connected by a non-return valve consisting of a flexible llap 26, to a longitudinal passage 27 inside the piston rod, so that the fluid pressure inside a space 28 between the tube 23 and piston rod 3a and hence 'the size of the clearance 25 can be accurately adjusted by means of a itiller connection not shown in the drawing. The headed reinforced edges of the flexible tube 23 press closely against the piston rod 3a due to their own pretension and the pressure of the sealing rings 29, 30.

Between the discs 19 and 20 there is provided a mass of resilient compressible material 11a of approximately ring shape in cross section and composed of a foam artiicial material as for example of polyurethane foam whose pore volume is measured so that at least a part will compensate the volume of the piston rod and simultaneously at least partly will compensate for the expansion due to temperature variations of the damping liquid. The ttoamvmaterial cushion 11a is enclosed by an outer casing 1 3 and an inner casing 13a around the piston rod 3a and the part, that is the inner part 13a, has openings 14, 15 and 16 therein. The openings 14 and 15 are closed by ap valves 17 and 18 which move upwardly and downwardly by the disc :as plate-like single pistons 19 and 20 to limit the through flow openings 21 and 22. The control of the iluid flow from one side of the piston to the other and thereby regulating the damping characteristics, operates the flexible element 23 with the medium being a iluid, air or a gas in the flexible element. Between the ilexible tube element 23 and the inner surface of the inner housing part 13a, the damping uid operates under damming pressure of the fluid at the definite temperature of the damrning medium through a slot of a definite size. If the temperature of the damping medium rises, the medium in tube element 23 will also expand so that the clearance 25 will become smaller at the same damping pressure. 'llhe apertures 16 in the inner wall of casing 13a are also used for the regulation of the dashpot characteristic in that Ilthey provide an additional bypass for the dampin-g liquid apart from the passages 15 and 22. Action of the dashpot can therefore largely be determined by suitable arrangement of these apertures, their number, size and location at diferent heights, without disadvantageous effect on the tempera-ture compensation provided by the flexible tube 23.

I claim:

1. A single tube hydraulic shock absorber comprising in combination, a cylinder having cylindrical walls, a piston rod, spaced piston heads secured to said rod and movable therewith relative to said cylinder within the latter, said cylinder having a movement damping liquid therein, a mass of resilient compressible material located between said piston heads and exposed to the pressure of said liquid, a container for said material whereby the latter is held away from said wall and said rod, a gas lled tube of resilient material disposed concentrically around said rod land having its ends maintained by tension in close contact with said rod, and a iller connection for said tube, said rod having therein a passage in communication with said connection and accessible externally 3,132,725 E 4 to claim 1, in which a said passage therein tterminates in References Cited in the le of this patent a flexible flap in the space between the tube and the rod.

4. A single tube hydraulic `shock absorber according to UNITED STATES PATENTS with the inside space of the casing. 

1. A SINGLE TUBE HYDRAULIC SHOCK ABSORBER COMPRISING IN COMBINATION, A CYLINDER HAVING CYLINDRICAL WALLS, A PISTON ROD, SPACED PISTON HEADS SECURED TO SAID ROD AND MOVABLE THEREWITH RELATIVE TO SAID CYLINDER WITHIN THE LATTER, SAID CYLINDER HAVING A MOVEMENT DAMPING LIQUID THEREIN, A MASS OF RESILIENT COMPRESSIBLE MATERIAL LOCATED BETWEEN SAID PISTON HEADS AND EXPOSED TO THE PRESSURE OF SAID LIQUID, A CONTAINER FOR SAID MATERIAL WHEREBY THE LATTER IS HELD AWAY FROM SAID WALL AND SAID ROD, A GAS 